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<div class="titlepage"><div><div><h4 class="title">
<a name="boost_asio.reference.write.overload12"></a><a class="link" href="overload12.html" title="write (12 of 16 overloads)">write (12 of
        16 overloads)</a>
</h4></div></div></div>
<p>
          Write a certain amount of data to a stream before returning.
        </p>
<pre class="programlisting"><span class="keyword">template</span><span class="special">&lt;</span>
    <span class="keyword">typename</span> <a class="link" href="../SyncWriteStream.html" title="Buffer-oriented synchronous write stream requirements">SyncWriteStream</a><span class="special">,</span>
    <span class="keyword">typename</span> <span class="identifier">Allocator</span><span class="special">,</span>
    <span class="keyword">typename</span> <a class="link" href="../CompletionCondition.html" title="Completion condition requirements">CompletionCondition</a><span class="special">&gt;</span>
<span class="identifier">std</span><span class="special">::</span><span class="identifier">size_t</span> <span class="identifier">write</span><span class="special">(</span>
    <span class="identifier">SyncWriteStream</span> <span class="special">&amp;</span> <span class="identifier">s</span><span class="special">,</span>
    <span class="identifier">basic_streambuf</span><span class="special">&lt;</span> <span class="identifier">Allocator</span> <span class="special">&gt;</span> <span class="special">&amp;</span> <span class="identifier">b</span><span class="special">,</span>
    <span class="identifier">CompletionCondition</span> <span class="identifier">completion_condition</span><span class="special">,</span>
    <span class="identifier">boost</span><span class="special">::</span><span class="identifier">system</span><span class="special">::</span><span class="identifier">error_code</span> <span class="special">&amp;</span> <span class="identifier">ec</span><span class="special">,</span>
    <span class="identifier">constraint_t</span><span class="special">&lt;</span> <span class="identifier">is_completion_condition</span><span class="special">&lt;</span> <span class="identifier">CompletionCondition</span> <span class="special">&gt;::</span><span class="identifier">value</span> <span class="special">&gt;</span>  <span class="special">=</span> <span class="number">0</span><span class="special">);</span>
</pre>
<p>
          This function is used to write a certain number of bytes of data to a stream.
          The call will block until one of the following conditions is true:
        </p>
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
              All of the data in the supplied <a class="link" href="../basic_streambuf.html" title="basic_streambuf"><code class="computeroutput"><span class="identifier">basic_streambuf</span></code></a> has been written.
            </li>
<li class="listitem">
              The completion_condition function object returns 0.
            </li>
</ul></div>
<p>
          This operation is implemented in terms of zero or more calls to the stream's
          write_some function.
        </p>
<h6>
<a name="boost_asio.reference.write.overload12.h0"></a>
          <span class="phrase"><a name="boost_asio.reference.write.overload12.parameters"></a></span><a class="link" href="overload12.html#boost_asio.reference.write.overload12.parameters">Parameters</a>
        </h6>
<div class="variablelist">
<p class="title"><b></b></p>
<dl class="variablelist">
<dt><span class="term">s</span></dt>
<dd><p>
                The stream to which the data is to be written. The type must support
                the SyncWriteStream concept.
              </p></dd>
<dt><span class="term">b</span></dt>
<dd><p>
                The <a class="link" href="../basic_streambuf.html" title="basic_streambuf"><code class="computeroutput"><span class="identifier">basic_streambuf</span></code></a> object from
                which data will be written.
              </p></dd>
<dt><span class="term">completion_condition</span></dt>
<dd>
<p>
                The function object to be called to determine whether the write operation
                is complete. The signature of the function object must be:
              </p>
<pre class="programlisting"><span class="identifier">std</span><span class="special">::</span><span class="identifier">size_t</span> <span class="identifier">completion_condition</span><span class="special">(</span>
  <span class="comment">// Result of latest write_some operation.</span>
  <span class="keyword">const</span> <span class="identifier">boost</span><span class="special">::</span><span class="identifier">system</span><span class="special">::</span><span class="identifier">error_code</span><span class="special">&amp;</span> <span class="identifier">error</span><span class="special">,</span>

  <span class="comment">// Number of bytes transferred so far.</span>
  <span class="identifier">std</span><span class="special">::</span><span class="identifier">size_t</span> <span class="identifier">bytes_transferred</span>
<span class="special">);</span>
</pre>
<p>
                A return value of 0 indicates that the write operation is complete.
                A non-zero return value indicates the maximum number of bytes to
                be written on the next call to the stream's write_some function.
              </p>
</dd>
<dt><span class="term">ec</span></dt>
<dd><p>
                Set to indicate what error occurred, if any.
              </p></dd>
</dl>
</div>
<h6>
<a name="boost_asio.reference.write.overload12.h1"></a>
          <span class="phrase"><a name="boost_asio.reference.write.overload12.return_value"></a></span><a class="link" href="overload12.html#boost_asio.reference.write.overload12.return_value">Return Value</a>
        </h6>
<p>
          The number of bytes written. If an error occurs, returns the total number
          of bytes successfully transferred prior to the error.
        </p>
</div>
<div class="copyright-footer">Copyright © 2003-2025 Christopher M.
      Kohlhoff<p>
        Distributed under the Boost Software License, Version 1.0. (See accompanying
        file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
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